Instruments to measure certain electrical quantities produced by multi-phased power generators have been developed and applied over the years as analytical tools to improve and maintain the efficiency and operating capabilities of these machines. Among such instruments are those which measure instantaneous power, reactive power, the unbalanced component of power, and the negative sequence current which results from an unbalanced load condition. For these four quantities, on a three-phase dynamoelectric machine, five operating parameters are useful as instrument inputs. These include the difference in voltage between each of two of the phases and the remaining third phase, and the three load currents, i.e., one for each phase.
Heretofore, such performance checks or calibration procedures have been possible only by making a laborious and time-consuming series of secondary measurements followed by calculations of results which were then compared to the quantities being measured directly. This requirement has seriously detracted from the utility and convenience of having instruments such as those mentioned above. In addition, the difficulty of acquiring the secondary measurements simultaneously, significantly affects accuracy since some quantities are susceptible to change as information on other quantities is being acquired.
It is therefore a principal object of the present invention to provide a calibration signal source by which the accuracy of instruments to measure instantaneous power, reactive power, the unbalanced component of power, and the negative sequence current of an operating dynamoelectric machine can quickly and reliably be established.
It is a further object of this invention to provide a calibration source for instruments to measure such parameters in a manner whereby calibration signal values are available simultaneously.
Still further objects will be apparent to those skilled in the art from the ensuing description of the principles and operation of the invention.